The present invention is directed to catalytic steam reforming of hydrocarbons. More particularly, the present invention is directed to a method for steam reforming of hydrocarbons, especially sulfur-containing hydrocarbons, using a sulfur-tolerant catalyst, and an apparatus therefor.
Steam reforming is a process whereby a hydrocarbon is reacted with high temperature steam to form hydrogen, carbon monoxide, and carbon dioxide. The product gas can be reacted as a fuel or used in chemical processing.
Hydrocarbons which can be reacted according to the present invention include methane, natural gas (including landfill gas) and heavier hydrocarbons (including diesel and jet fuel).
Potential hydrocarbon feeds for the reforming process often contain large quantities of sulfur. Gas oil, for example, may contain as much as 1500 ppm sulfur. As described in greater detail below, reforming of sulfur-containing hydrocarbons can lead to increased expense.
Typically, catalytic steam reforming of natural gas or heavier hydrocarbon feeds is achieved by using a nickel catalyst. However, due to the extreme sensitivity of nickel metal to sulfur-containing compounds, which are a severe poison to the nickel catalyst, the hydrocarbon feed must generally be purified of sulfur, to less than 1 ppm, prior to steam reforming. This requirement results in additional expense for the hydrocarbon steam reforming process. Furthermore, whereas light fractions may be amenable to hydrodesulfurization, desulfurization of heavy fractions is extremely difficult.
An alternative is to use the nickel catalyst for hydrocarbon steam reforming and allow it to be poisoned by the sulfur, but to operate at higher temperatures and with higher volumes of catalyst to counteract the loss of catalyst activity due to poisoning. This alternative also results in additional cost and weight to the process.
A second alternative is to use noble metal catalysts, such as platinum, palladium, or rhodium in place of nickel. While the noble metal catalysts are very active for steam reforming and are somewhat tolerant of sulfur-containing feeds, they are very impractical because of their high cost.
Therefore, a clear need exists for a steam reforming apparatus containing a catalyst which is highly tolerant of sulfur, and which does not add significantly to the cost of using nickel catalysts.